Flying Circus

My 03 3500 pulling around 12,000 pounds.....Smarty on tow/haul, silverline 4" straight pipe, 22.5 rims with 10r22.5 goodyears, 3.73 ring and pinion with a nv4500 5 speed....usually pull in 4th gear at 60 mph with 1900 rpms?? What should I expect for fuel mileage?? Wondering if a gear change will improve mileage, it's also sluggish on overpasses, should I turn the smarty up?? EGT's never above 1100 Here's a pic......

Jeff in TD

I would guess you might get around 11 towing that?

What speed you run will have a huge effect on fuel efficiency. 7 or 8 mph can make or take several MPG.

MikeyB

Hate to say this but the best solution is going back to smaller diameter wheels/tires.

MikeyB

Colo_River_Ram

You need new gears (I doubt he will get rid of the tires and rims) 4:10 minimum if not deeper..

Flying Circus

I talked to Randy's Ring and Pinion, they recommended a Yukon gear set, 4.56 with a grizzly locker for the rear and installation kits front and rear. This was close to 2k, a lil spendy but if it will bring me back to stock power and shift ratios I think it would be a good investment, that being said the truck drives awesome empty I get 75-78 mph at 1900-2000 rpm in 5th gear, but haven't been on a long trip empty to see how good the fuel mileage is, Pulling the boat the estimate was dead on anywhere from 11-13.5 mpg.....How much increase in fuel mileage would I see going with the 4.56 when pulling the boat? I know there's a lot of wind drag and the added weight of the rims and tires, just curious how beneficial it will be to drop the 2k.....
Thanks

Colo_River_Ram

I don't see the need for a locker in the rear myself.. with those tires on a dually you are not going 4 wheeling with it.. The R&P should have been done with the tire swap.. or at least that is my opinion on the subject..

HMX-1

Wow those tires are huge! I would skip the 4.10's and go straight to 4.56's.



Kris

sewman

How often do you pull the boat?I doubt if your mpg will improve pulling the boat w/a gear change& @ 75 empty you'll be running higher rpm

Flying Circus

Pretty much what I was thinking just looking for some confirmation......
Thanks

C Schomer

Your existing gearing sounds pretty good. Tow in direct and don't punish the OD and save OD for empty but the rpm spread between gears must be HUGE. I wouldn't expect better mpg but the lower R&P will put your gears closer together and make 1st gear much better for creeping. I had a 97 5spd 3.54 and it sucked whenever I moved really heavy trailers for friends. 1st gear could hardly be called "granny"! Craig

CoastalDav

I figure your rear ratio is very close to 3:00-1 with the 22.5 tires to get 60 mph at 1900 rpm's in 4th.

I agree with the other guys on the rear gear change to get your rpms up so you can run in 4th or 5th as long as your going to keep the 22.5's on the truck.

My truck pulls combined 23,000lbs at 10.5 to 11mpg with the Juice/Attitude on the Tow Position. Running lite, 19 mpg at 68 mph Juice on Stock position.

Dave

etn550

Big tires and lifted trucks go against fuel economy. More mass to get moving and more air resistance. No way around that. Your mileage seems reasonable for what you have and better than some. Since you are 4x4 I would skip the limited slip. Do you use 4x4 on the boat ramps? I had some big boats with tri-ax trailers. The boat ramps can get pretty slippery when you got over 10,000 to get out of the water. I'm getting around 13 towing a 30ft travel trailer with the truck in my sig and am happy with that. I usually go around 63mph on the hwy.

JHardwick

I want to know how you managed a NV4500 in an '03?

pdogg

Sorry, every time I see a truck with those wheels like that it reminds me of this...

MikeyB

The NV4500 is the standard transmission when coupled to the SO (235-250hp) CR Cummins.

MikeyB